Carbonate Ores

What is Carbonate Ores?

A carbonate is a salt of carbonic acid (H2CO3). The formula of carbonate ion is CO3−2. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock.

Carbonates are moderately strong bases. Aqueous solutions are basic because the carbonate anion can accept a hydrogen ion from water. CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻ .It reacts with acids, forming salts of the metal, gaseous carbon dioxide, and water

The most common carbonate ores are calcite or calcium carbonate, CaCO3, the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite, a calcium-magnesium carbonate CaMg(CO3)2; and siderite, or iron(II) carbonate, FeCO3, an important iron ore.

The carbonates have several important uses: Ca carbonates in the manufacture of cement, dolomite in refractory materials, and siderite and rhodochrosite as sources of iron and manganese.

Table of Contents

• List of Carbonate Ore
• Carbonate ore of Copper
• Carbonate ore of Calcium
• Carbonate ore of Magnesium
• Carbonate ore of Zinc
• Carbonate ore of Iron
• Frequently Asked Questions

List of Carbonate Ore

Carbonate ore of Copper

• Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2
• This is an opaque, green-banded mineral.
• Malachite crystallizes in the monoclinic system. The structure consists of chains of alternating Cu²⁺ ions and OH⁻ ions, with a net positive charge, woven between isolated triangular CO₃²⁻ ions. 
• Thus each copper ion is conjugated to two hydroxyl ions and two carbonate ions; each hydroxyl ion is conjugated with two copper ions; and each carbonate ion is conjugated with six copper ions.
• Malachite often results from the supergene weathering and oxidation of primary sulfide copper ores, and is often found with azurite (Cu₃(CO₃)₂(OH)₂), goethite, and calcite.
• Simple methods of copper ore extraction from malachite involved thermodynamic processes such as smelting. This reaction involves the addition of heat and a carbon, causing the carbonate to decompose leaving copper oxide and an additional carbon source such as coal converts the copper oxide into copper metal.
• Malachite is also used for decorative purposes, such as in the Malachite Room in the Hermitage Museum.

Carbonate ore of Calcium 

• Calcite is a carbonate mineral of Calcium with the formula CaCO₃.
• Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. 
• Calcite, like most carbonates, will dissolve in acids via the reaction

CaCO₃(s) + 2H⁺(aq) → Ca²⁺(aq) + H₂O + CO₂(g)

• The calcite in limestone often contains a few percent of magnesium. Calcite in limestone is divided into low-magnesium and high-magnesium calcite.
• Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms.
• Microbiologically precipitated calcite has a wide range of applications, such as soil remediation, soil stabilization and concrete repair.
• A transparent variety of calcite known as Iceland spar may have been used by Vikings for navigating on cloudy days

Carbonate ore of Magnesium

• Magnesite is a mineral with the chemical formula MgCO₃ (magnesium carbonate)
• It consists of white trigonal crystals. The anhydrous salt is practically insoluble in water, acetone, and ammonia. All forms of magnesium carbonate react with acids.
• It can also be formed via the carbonation of magnesium serpentine (lizardite) via the following reaction:

2 Mg₃Si₂O₅(OH)₄ + 3 CO₂ → Mg₃Si₄O₁₀(OH)₂ + 3 MgCO₃ + 3 H₂O

• Magnesite can be cut, drilled, and polished to form beads that are used in jewelry-making. Magnesite beads can be dyed into a broad spectrum of bold colors, including a light blue color that mimics the appearance of turquoise.

Carbonate ore of Zinc

• Smithsonite, also known as turkey fat or zinc spar, is the mineral form of zinc carbonate (ZnCO₃)
• Smithsonite is a variably colored trigonal mineral which only rarely is found in well formed crystals. The typical habit is as earthy botryoidal masses. 
• Smithsonite occurs as a secondary mineral in the weathering or oxidation zone of zinc-bearing ore deposits.

Carbonate ore of Iron

• Siderite is a mineral composed of iron(II) carbonate (FeCO₃).
• Siderite is also the name of a type of iron meteorite.
• It crystallizes in the trigonal crystal system, and is rhombohedral in shape.
• Its colour ranges from yellow to dark brown or black, the latter being due to the presence of manganese.
• The carbonate ore is more difficult to smelt than a haematite or other oxide ore
• Siderite is antiferromagnetic below its Néel temperature of 37 K which can assist in its identification